Man admits role in fiery attack on teen

A second man has admitted his role in setting an Adelaide teenager on fire in an unprovoked attack described as "cowardly, vicious and terrifying".

In the South Australian District Court on Monday Tristan Dale Champion pleaded guilty to recklessly causing serious harm to Luke Coburn, who suffered burns to 28 per cent of his body in January 2013.

The instigator of the attack, Joshua William Lomas, was jailed for five years over the incident, which stemmed from Lomas becoming jealous that his girlfriend had started seeing Mr Coburn, who was only 17 at the time.

Lomas hatched a plan to throw flammable liquid and set it alight in the open garage where the victim was relaxing with a friend.

But the court heard on Monday that it was not Champion's idea to make the Molotov cocktail and he had no beef with Mr Coburn.

"Basically, he just stupidly went along with Lomas thinking it was going to be a car that was torched," defence counsel Lindy Powell said.

"The whole plan changed literally in the split second before the petrol was thrown at Lomas."